SPC MD 507

SPC MD 507


Mesoscale Discussion 0507
NWS Storm Prediction Center Norman OK
0252 PM CDT Tue Apr 23 2024

Areas affected…Northeast Illinois and southeast Wisconsin into
central Lower Michigan

Concerning…Severe potential…Watch unlikely

Valid 231952Z – 232145Z

Probability of Watch Issuance…5 percent

SUMMARY…Isolated to scattered thunderstorms will continue to
develop across the Great Lakes region. A few strong to severe storms
are possible with small to marginally severe hail and damaging winds
as the primary hazards. Coverage of severe storms should remain
sufficiently limited to preclude watch issuance.

DISCUSSION…Isolated to scattered thunderstorms have been ongoing
over eastern WI, the Upper Peninsula of MI, and northern WI over the
past several hours with multiple reports of 0.5 to 0.75 inch hail
and 35-45 knot gusts noted. This convection has largely been driven
by ascent along and ahead of a secondary cold frontal surge where a
combination of modest diurnal warming and cold temperatures aloft is
supporting MUCAPE between 250-500 J/kg. This trend is expected to
continue downstream into IL/MI as the cold temperatures aloft
overspread the region and mid/upper-level cloud cover slowly shifts
southeast. Based on recent observations and RAP forecast soundings,
around 500 J/kg MUCAPE should be feasible as surface temperatures
warm into the upper 60s. Weak mid-level winds to the north of a jet
streak over IL/IN/OH have limited storm longevity/organization thus
far, but destabilization closer to the stronger mid-level flow may
promote higher, though still somewhat meager, effective bulk shear
values between 20-25 knots. This should support better storm
organization with a higher potential for marginally severe hail (0.5
to 1.0 inch) and localized damaging wind gusts (most likely between
40-50 knots). Latest mesoanalysis suggests a higher buoyancy axis
exists from southeast WI into west-central/northern Lower MI, so the
severe threat may be maximized across this corridor in the coming
hours. However, severe thunderstorm coverage should remain limited
given the overall marginal kinematic environment.

..Moore/Smith.. 04/23/2024

…Please see www.spc.noaa.gov for graphic product…


LAT…LON 42488950 43578801 44268639 44628527 44778397 44328368
43908355 43568358 43318386 42828463 42128642 41808735
41608809 41558865 41568906 41568926 41978954 42178960

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